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Optimized superconducting detectors using the proximity effect in Ti/TiN multilayers



David P. Pappas, Michael R. Vissers, Jiansong Gao, Martin O. Sandberg, David S. Wisbey, Kent D. Irwin


We apply the superconducting proximity effect in TiN/Ti multi-layers films to tune the critical temperature, $T_C$ (to within 10 mK) with high uniformity (less than 15 mK spread) across a 75 mm wafer. Reproducible $T_C$'s are obtained from 0.8 - 2.5 K. These films had high resistivities, $\ge 100$ $\mu \Ω$-cm and internal quality factors on the order of 100k and higher for resonators in the GHz range. Both trilayers of TiN/Ti/TiN and thicker multilayer films were prepared, demonstrating a highly controlled process for films from less than 15 nm to at least 60 nm thick. Detectors were fabricated and showed single photon resolution at 1550 nm. The high uniformity and controllability coupled with the high quality factor, kinetic inductance, and inertness of TiN make these films ideal for use in frequency multiplexed kinetic inductance detectors and other potential applications such as nano-wire detectors, transition edge sensors and associated quantum information applications.
Applied Physics Letters


Kinetic inductance sensors, superconductivity, resonators, single photon
Created June 14, 2013, Updated November 10, 2018